Proto-organelles are prokaryotic structures that compartmentalize important compounds or chemical reactions, functioning similarly to eukaryotic organelles. For instance, some carboxysomes are considered proto-organelles because they sequester functionally related enzymes in a specific cellular location.

Proto-organelles

Carboxysomes are cytoplasmic inclusions composed of an outer shell made of thousands of protein subunits. Produced by cyanobacteria like Anabaena cylindrica and other bacteria such as Halothiobacillus neapolitanus, their interior is filled with carbonic anhydrase and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) for use in carbon metabolism.

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Cytoplasmic inclusions are structures often found in prokaryotic cells that serve to compartmentalize their cytoplasm, despite their general lack of complex membrane-bound organelles. They can store nutrients or gas needed for the cell's metabolism or buoyancy, and they play an important role in reducing the buildup of osmotic pressure as the cell accumulates compounds.

Cytoplasmic Inclusions

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

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Glycogen and starch inclusions are cytoplasmic structures found in some prokaryotic cells that store excess carbon in a polymerized form. Cells can access these stored polymers for energy when needed. Storing these nutrients in a polymerized state is advantageous because it prevents the buildup of osmotic pressure that would otherwise occur if the cell accumulated individual solute molecules.

Glycogen and Starch Inclusions

Volutin granules, also known as metachromatic granules due to their staining characteristics, are a type of cytoplasmic inclusion that stores polymerized inorganic phosphate. This stored phosphate can be utilized in cellular metabolism and assists in the formation of biofilms. These granules are found in various microbes, including the archaea Methanosarcina, the bacterium Corynebacterium diphtheriae, and the unicellular eukaryotic alga Chlamydomonas.

Volutin Granules

Sulfur granules are a type of cytoplasmic inclusion found in certain sulfur bacteria, such as those in the genus Thiobacillus. These granules store elemental sulfur, which the bacteria can subsequently utilize for their metabolism.

Sulfur Granules

Polyhydroxybutyrate (PHB) inclusions are specialized cytoplasmic storage structures that are surrounded by a phospholipid monolayer embedded with proteins. These inclusions are produced by certain bacterial species, such as Bacillus and Pseudomonas. In industrial applications, the PHB harvested from these inclusions is utilized as a source of biodegradable polymers to manufacture bioplastics.

Polyhydroxybutyrate (PHB) Inclusions

Gas vacuoles are accumulations of small, protein-lined vesicles of gas found in some prokaryotic cells. These inclusions allow the cells to alter their buoyancy, enabling them to adjust their vertical location within a water column.

Gas Vacuoles

Magnetosomes are cytoplasmic inclusions found in magnetotactic bacteria, such as Magnetospirillum magnetotacticum. They consist of magnetic iron oxide or iron sulfide surrounded by a lipid layer, which allows the cells to align along a magnetic field to aid their movement.

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